Tube



Feb. 1, 1944. w w n-E 2,340,460

TUBE

Original Filed Feb. 11. 1942 INVENTOR. MLL/AM W 57751.

H15 ATTORNEY Patented Feb. 1, 1944 direct and mesne assignments, to Eitel-Mc- Cullough, Inc., San Bruno, Calif., a corporation of California Original application February '11, 1942, Serial No. 430,387. Divided and this application May19,

1942, Serial No. 443,637

1 Claim. (01. 250 -275) This is a division of my copending application, Serial No. 430,387, filed February 11, 1942, in which is claimed the method embodying the improvements of my invention, while this application is particularly directed to the article produced by my method.

My invention relates to the manufacture of vacuum tubes; and more particularly to improvements in the construction and fabrication of tubes adapted for high frequency work.

It is among the objects of my invention to provide a tube having a lead of relatively large cross section extending through an envelope and having an inner end terminating close to the envelope wall to provide a short heavy lead for conducting high frequency current.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of my invention. It is to be understood that I do not limit myself to this disclosure of species of my invention, as I may adopt variant embodiments thereof within the scope of the claim.

Referring to the drawing;

Figures 1 and 2 are side views, partly in section and partly in elevation showing portions of a vacuum tube illustrating the improved structure and method embodying my invention; and

Figures 3, 4 and 5 are similar views illustrating a modified tube structure and method of making the same.

In terms of broad inclusion, my improved tube comprises a. lead extending through and sealed to the wall of the envelope, with the inner end of the lead terminating close to the envelope wall; and an element fixed or welded to the inner end of the lead. In one form of my invention the end of the lead is flush with the inner surface of the envelope, giving the shortest possible lead. The element referred to as being fixed to the lead may be an electrode or any other internal tube part.

In greater detail, and referring to Figures 1 and 2 of the drawing, my improved method comprises sealing a relatively heavy lead 2 of suitable material, such as tungsten, to a glass envelope 3. The lead may be sealed to the envelope in accordance with the usual procedure of sealing a glass bead 4 to the lead, positioning the beaded lead in a flared opening 6 of the envelope, and then fusing the bead to the envelope by applying a flame I, as shown in Figure 1. The bead and envelope both being of similar material, namely glass, readily fuse together to form the seal. Any suitable glass having the desired expansion and other required characteristics may be employed for the 'the extreme end of lead ll.

bead and envelope. Nonex glass is preferablyused for the envelope, and uranium 'glassis preferably used for the bead.

In order to keep lead 2 as short as possible, bead 4 is applied fairly close to the end of the lead, so that after the seal is made the inner end of the lead terminates close to envelope wall. As a comparative measure, the end of the lead preferably extends beyond the inner face of the envelope at the seal a distance not greater than the diameter of the lead.

After sealing in the lead the parts are cleaned in any suitable manner to remove oxides formed during the sealing process.

An internal element of the tube, such as anode supporting bracket 8, is then fixed to the inner end of the lead. In Figure 2 I show an anode 9 having an end cap ll carrying the supporting bracket 8; these parts being preferably assembled as a unit ready for fastening to lead 2. It is understood however that this internal structure is merely for purposes of illustration, and that element 8 may be a support or connector for some other tube part.

Element 8 is preferably fixed to the short inner end of the lead by welding. This is accomplished by establishing electrical connections with the element and with the lead at the outer side of the envelope to pass a Welding current through the element and lead. For this purpose a terminal l2 of a suitable welding circuit is secured to the outer end of lead 2. The other leg of the welding circuit is connected to an electrode I3 adapted to make contact with element 8 at a point opposite lead 2.

Electrode l3 may be of any suitable shape. For use with the anode structure illustrated, the electrode preferably has a reduced end portion H for insertion through an aperture in cap II to reach the inner surface of bracket element 8. A centering flange it on the body of the electrode provides means for properly positioning the anode structure. By this arrangement the prefabricated anode unit may be slipped on the end of the welding electrode and the whole moved up into the envelope to bring element 8 into contact with the end of lead 2. After making the weld, electrode I3 is withdrawn and terminal I2 is removed.

In the modified structure and method illustrated in Figures 3 to .5, a bead I6 is sealed to The beaded end of the lead is then pressed into contact with the outer face of envelope l8 in the presence of flame I9 a suitable anvil 2| having a concave depression 22 at the nose being brought against the inner face of the envelope to permit application of pressure without breaking the glass. The heat fuses bead l6 to the envelope, and under pressure lead I! sinks into the envelope wall as shown in Figure 4, leaving only a thin film of glass over the end of the lead at the inner face of the envelope.

The film is then removed, preferably by press-. ing a grinding wheel 23 against the inner face of the envelope below the lead. Removal of the glass film exposes the inner end of the lead, and

provides a structure in which-the exposed end ment 24 is butt welded to the lead; suitable terminals 26 of a welding circuit being connected to the element and to the lead at the outer side of the envelope. Of course element 24 could be a supporting bracket of the character shown in Figure 2, in which case a suitable welding electrode would be employed to make the necessary connections.

I I claim:

L A tube comprising an envelope having a glass Wall, a solid metal lead extending through the wall with its inner end terminating close to the inner face of the Wall and its outer end projecting beyond the outer face of the wall, a glass bead sealed to the lead and fused to said glass wall at the point where the lead projects therethrough, an internal part of the tube disposed within the envelope, and supporting means comprising a hollow bracket having one end secured to said part and the other end welded to the inner end of said lead.

WILLIAM W. EITEL. 

